German Patent Application DE 42 20 854 A1 discloses a prior art rim brake. In this brake, the hydraulic cylinder is disposed substantially horizontally, so as to be fastened with one end to the right arm and with the other end to the left arm. As a result, this brake has a large structural space and poor aerodynamics with a large amount of air turbulence. Furthermore, this rim brake has the disadvantage that, during installation on the vehicle, in some installation situations, the brake line must be dismounted from the master unit and/or slave unit and brake fluid can escape from the then free end of the hydraulic line. In this situation, cumbersome deaeration is necessary.